Finishing for Non-Finishers, Part V


Before you begin…STOP!

Careful assembly and surface preparation go a long way to making your finishing techniques pay off.  Said differently, no finish can (or will) cover up every blemish you might leave by not preparing the surface carefully.  In fact, most experienced woodworkers would agree that applying a finish tends to magnify poor surface prep rather than conceal it.  That’s why the first four posts in this series haven’t talked about actually applying the finish.  And that’s why this one starts the way it does.

It’s not too late.  You can still give the surfaces one last, careful examination before you start with the finishing.

Okay, Here We Go

Get out the Sample Boards

Once you’re certain all of the blemishes, scratches, swirls, glue squeeze-out and the rest of it are gone, (and this includes your sample boards, by the way) it’s time to work out your “finishing schedule”.  That’s my term, and it doesn’t imply the timing of the steps, but rather the steps themselves.  And all of the work is going to get done first on the sample boards you’ve saved from the project. While it might seem like a ton of additional effort, working out your finishing steps on project remnants will pay dividends in several ways.

First, it saves the project from ruin.  Unless you have used the proposed sequence of colorants and topcoats before, you don’t really know how they will look on your finished project.  The worst possible outcome is that the finish doesn’t provide you the look you had in mind when you began, or that the finish really does damage the appearance of the project.  In the latter case, I refer to instances like pigment stains on pine, or certain oils on cherry, both species that are prone to significant blotching.  If blotches are the look you’re after, terrific – but better to know your wood is going to react this way before hitting the actual project with the stain.

Second, as you build up your finishing samples, you’re building a library of sorts.  Assuming you keep clear notes about your finishing sequence (more on this in a minute) you can refer back to your library when you’re working on the next project and pick out a sample that offers you the look you’re after.  You will build up familiarity with different finishing products and determine what works well in your own shop.  Here is an assortment of the sample boards from my shop, front and back:

Finishing Schedule Notes

There are any number of ways you can record the steps you’ve taken as you develop your finishing schedule.  Use note cards, a spiral-bound notebook, or do what I do:  record your work directly on the back of the sample.  No matter how you record your work, write down every step in detail.  A small detail like a change in sanding grit can make a difference in your end result.  One small shortcut is to develop shop standards – steps that you perform the same way each and every time you execute them.  For example, in my shop, “scuff sand” means P320 grit paper held in my hand.  So I save a few pen strokes there.  Recording the process on the sample saves me from searching through the shop for the particular card I need to re-create a finish.

At the beginning of this series, I suggested that the time to chose a finish was before you started work.  If you have done that, you’re ahead of the game. If you haven’t yet made those decisions, now’s the time.  Since this series is aimed at non-professional finishers and woodworkers, my advise is to keep things simple at the beginning.  That’s why plain shellac is the first finish I’m going to suggest you get acquainted with.

Getting to Know Shellac

As a top coat, shellac has a lot going for it, which is why it has been around for so long.  It’s natural and non-toxic.  You’ve probably eaten it more than a few times: ever wonder what makes the outside of M & M’s so smooth and shiny?  You’ve probably seen someone wearing it in their hair, too.  Ever wonder what finish preserves the American furniture in the Smithsonian?  There are a lot of reasons its popularity has lasted.  I recently grabbed a few apple boxes from my local grocery store, and guess what is printed on the bottom!

A family-friendly finish....

For the beginning finisher, shellac has a number of other benefits.  Because its solvent is alcohol, each succeeding coat dissolves the preceding one, and they essentially “melt” together.  So as you add coats, you’re really not building one coat on top of another with discrete borders in between.  Instead, you’re just making one layer thicker and thicker.   If you decide that you have really messed up the job and need to start over, a thorough soaking with alcohol will return the shellac to solution and you can wipe it off the surface and start over.  This means that the finish is easily repaired, too.  Of course, being alcohol-soluble has at least one strong drawback: if you spill an adult beverage on this finish, it can be damaged unless you clean it up immediately.  Clearly this could be a limitation for a tabletop, but for boxes, bedroom furniture (dressers, bed frames and so on) shellac might be all you need.  Finally, because you aren’t using any drying oils, there is no risk of spontaneous combustion from oil-soaked rags.  You do, however, want to provide plenty of ventilation to disperse the alcohol fumes, which are flammable and can be explosive in high enough concentrations.

Shellac has several other useful properties that endear it to finishers, professional and amateur.  Diluted concentrations of shellac are often used as a “wash coat” on bare wood.  Depending on the amount of shellac dissolved in the alcohol, the “wash coat” controls (limits) the amount of coloring or penetrating finishes (like oils and pigment stains) that will absorb into raw wood.  For those blotch-prone species like pine and cherry, a dilute coating of shellac goes a long way to eliminating the problem.  More on this later in the post.

In the same way that shellac helps to seal bare wood, it can provide a barrier between different steps in a finishing sequence.  Say, for instance, that you have dyed a project with a water-soluble dye, and being environmentally friendly,  you decide to use a water-based topcoat.  A seal-coat of shellac in between the dye and the topcoat will prevent the water in the topcoat from re-dissolving the dye.  The uses go on and on, and your continued research and experimentation will produce more than I can write about here.

The November/December 2010 issue of Fine Woodworking magazine has a good article on the origins and processing of raw shellac.  It’s interesting reading.  For the purposes of this article, I’ll summarize and condense some of that information and more into a few short paragraphs.  The article is worth the read, if you have time and a subscription.

Raw shellac includes a component of wax, which all by itself is of no concern to a finisher.  However, when shellac with wax is used as an undercoat to some other finishes, there can be a problem with the succeeding layers adhering.  To address this issue, shellac manufacturers have “de-waxed” and then dried shellac into flakes that you can dissolve in alcohol, making your own concentrations of shellac as a finish right at home.  Along with the dewaxing process, the color of the flakes can be controlled, giving you the option of colors ranging from a warm honey-amber hue to nearly colorless.  These options provide you with a lot of control over how the shellac looks on the project.  Shellac can also be tinted, giving you even more precise control.  In its colorless state, it will do little to change the color of the project.

Shellac’s concentration is measured in the number of pounds of shellac dissolved into a gallon of alcohol.  This concentration is referred to as the shellac’s “cut”.  One pound of shellac flakes dissolved in one gallon of alcohol is known as a “one-pound cut”; two pounds as a “two-pound cut” and so on.  The amount of shellac in alcohol is an important factor for a finisher.  The more shellac in the solution, the more you’re applying with each coat and therefore the fewer coats you’ll need to build up the same film thickness on the project.  There is a drawback to using higher cuts of shellac: the higher the concentration, the harder it is to put on a streak-free coat by hand.  A three-pound cut is about as high a concentration as you’re likely to find, or want to mix yourself, and I think you would have better initial luck with a one- or two-pound cut.

Before you decide to start mixing your own finishes, here’s a time-saving suggestion.  Buy a quart (or a gallon) of a product called Seal-Coat, made by Zinsser.  This is a dewaxed shellac in a 2-pound cut, and it does a great job as that “barrier coat” I mentioned a few paragraphs above.  Finishers refer to this barrier as a “wash coat”.  If you’re going to apply a wash coat, dilute some Seal-Coat with an equal amount of isopropyl alcohol, which you’ll find at paint stores and in the paint departments of the big box stores.  Brush the mix on with a natural bristle or Taklon-bristle brush.  Work “off” the edges (in other words, start your stroke a few inches in from an edge and brush off the surface) and keep a wet edge.  Don’t rebrush or try to “tip off” the shellac – put it on and leave it alone.  When it’s dry (allow half an hour) gently scuff-sand the surfaces with P320 grit sandpaper, and you’re ready for the next step in your finishing schedule.

Shellac can also be used all by itself – not as a wash coat, but as the entire finish.  As I mentioned, it’s been used as a finish for hundreds of years.  If you plan to use shellac as the only finish for your project, it’s time to consider mixing your own.  More on that subject in the next post.

So, on your sample boards, either tape off sections or use a table saw, radial arm saw or cutoff saw to cut kerfs across the width of the sample.  Apply a thin coat of your shellac to all but one end section of the sample board.  The end section will be used to judge your first color layer without the benefit of a wash coat.  The rest of the board will start with the wash coat as the first step in the finishing sequence.

In the next post we’ll talk a little about color and the use of shellac as a final top coat.

Here are links to the first four posts in this series.

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II
Finishing for Non-Finishers, Part III
Finishing for Non-Finishers, Part IV
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Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon.  He is a frequent woodworking instructor and writer.

Categories: Woodworking | Leave a comment

Finishing for Non-Finishers, Part IV


Now we’re ready to do final assembly operations for the project.

Before you begin, I recommend that you do some serious housekeeping around your bench or your assembly area, if you have a separate spot. If you are like a lot of woodworkers, you might have a tool or two on your bench, along with some sawdust or shavings from your hand plane or scraper. Right now is the time to get all of the debris left over from your milling and smoothing operations cleaned up. Put away all of the tools, vacuum the bench top and the floor. You’re at the point in the project where significant care should be taken to maintain the surfaces you’ve worked hard to create. This additional care during assembly will pay off when you begin applying a finish.

Get your hands on some carpet remnants or a quilted moving blanket to cover your bench or assembly table. Even with a clean bench top, project components can (and do) slip out of your hands and a collision with a hard bench top can ding an edge or round a corner. A bit of padding on your work surface will help prevent damage.

Careful Clamping is Key

Clamping components together is a staple of the glue-up and assembly processes. But clamps can damage components if they’re not carefully applied, and if a big bar clamp slips or slides into your work, you have repair work ahead.

I  use four kinds of clamps in my shop. I have a lot of pipe clamps with Jorgensen heads. The nice thing about pipe clamps is the ability to change clamp length by moving the heads to different length pipe.  Over the years I have epoxied small squares of 1/4″ MDF with rounded edges to the faces of both clamp components,  rounded edges facing the component to be glued up. I have found that it is considerably easier to attach these clamping blocks or pads to the clamp than it is to struggle with loose clamping blocks, the clamps, the glue bottle, and the components. The alternative, which I did for a few years, is to tape clamping blocks to the components before gluing up. Eventually I wised up.  Here’s an image:

MDF pads epoxied to clamp fixtures

The second kind of clamp I use is a Bessey K-body in varying bar lengths. I like the performance of these clamps, but they are expensive, and limited by the length of the bar. I have not found the pads to mar or discolor surfaces, but if I am applying them to relatively soft woods, I will use a clamping block where needed.

The third clamp style is a Jorgensen F clamp, either the heavy-duty or “3700” style clamps.  I don’t use the light duty clamps for glue-ups because there is too much flex in the bar.  The heavy-duty style does an acceptable job in the right circumstances, with one caution: the factory-applied orange clamping pads will stain the work if they are left in place too long.  Some time ago, I removed these clamping pads and replaced them with MDF pads similar to those pictured above.  In my shop, the “3700” clamps are mostly utility clamps, and see limited duty during glue-ups.

The fourth and final style clamp is a wooden handscrew. These “old-fashioned” clamps can exert a tremendous amount of clamping pressure, and are really quite useful in the right application. They are limited by the size of the jaw opening, and so are not suitable for large-scale glue-ups.

There is at least one trait common to all of these clamps: they must be kept clean.  Furniture assembly is messy business.  Glue gets squeezed out of joints and panels, and some of it is going to find its way to your clamps.  Clean it off as soon as the glue-up is complete.  The drop you miss today will be the one that gets pressed into the surface of your next glue-up.  How do I know this?  If you’re clamping panels using pipe or bar clamps, it is sometimes helpful to put a short piece of masking tape on the bar or pipe directly below the joint being glued.  That way, squeeze-out can be easily removed when the glue-up is complete.

A Last Look and Some Housekeeping

Once the project is completely glued together, do a careful inspection of every surface. You’re looking for any errant glue squeeze-out, as well as any damage or marking caused by the clamps. The best way to look for these assembly remnants is with strong light from a window or from a set of halogen lamps on a stand. You want the light raking off the surface at a low angle and bouncing into your eyes. Take your time and look at every surface and joint. If you find glue use a scraper, a sharp chisel, or a dental pick to remove it. If you notice marks from the clamps, a light sanding or a touch-up with your scraper or hand plane should clean things up. Use care when manipulating the project to preserve all of the surface preparation work you have done. Keep the project on the moving blanket or carpet remnant as much as possible.

I like to clean the finishing area of the shop the night before I plan to apply finish. I will vacuum floors and work surfaces, and also vacuum the project. I also turn off the ceiling fans so that any bit of airborne dust have the chance to settle out of the air. I save the tack cloth for just before the first coat of finish goes on.

Now is the time to get out the project cutoffs mentioned earlier in this series. They should have been planed, scraped or sanded (or all of the above) just like the project components were. They should be vacuumed to clean up what dust has accumulated since you produced them.

In the next post we’ll start applying finish to the sample boards and evaluating the results.

Previous Posts in this Series:

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II
Finishing for Non-Finishers, Part III

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Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon. He is a frequent woodworking instructor and writer.

Categories: Woodworking | Tags: , , , , | Leave a comment

Finishing for Non-Finishers, Part III


Preparing Surfaces for Finishing

Hand Work Requires Thought

Let’s get down to some basic facts.  Lumber goes through a number of steps on the road to becoming a component in a piece of furniture.  Typically it is sawn, jointed and reduced in thickness.  Additional shaping operations might also be involved.  Each of these steps leaves a signature behind and those machine marks are not a decorative effect.  You really cannot leave them behind and later call them design features.  They all need to be removed.  How you accomplish that impacts how you finish, and what that finish looks like.  Woodworkers generally choose one of two options: cutting (hand planes, scrapers) or abrasion (sandpapers).  As a general rule, do as much of this work as you can after the joints are cut, but before gluing up.  It’s a whole lot easier, for example, to clean up the apron on a table or the rails on a chair before rather than after they’re glued into the legs.

Admitting my Bias

In the interest of full disclosure, I am mostly a hand-tool woodworker.  That is not to say that I don’t use power tools.  I use them whenever they make sense.  There are many times, though, when a hand tool does a  job faster, more safely, and give a better result.  So if the following comments lean a little in the direction of hand tools, you’ll know why.

A Case in Point: The Hand Plane

Students who have taken my classes know I hate sanding.  Detest it.  So I avoid sanding as often as possible.  There are a number of reasons I feel this way, but the one that relates most directly to finishing is that sanded wood and hand-planed (or scraped) wood looks different.  One surface has been abraded to make it smooth, and it looks hazy.  The other surface has been cut to make it smooth, and it looks clear.  If you don’t believe me, do the following demonstration for yourself.  Take a well-tuned hand plane with a sharp iron, and plane the surface of a piece of cherry or oak, or whatever hardwood you have on hand.  Plane it until the milling marks are gone and you have a nice smooth surface.  Now take a piece of sandpaper of the grit you would normally use last in a sanding progression.  Most woodworkers don’t (and shouldn’t) sand beyond P220 grit, so use that.  Sand half the board you just planed.  It will be smooth, for sure.  But look at the difference between the hand-planed surface and the sanded surface, and you will see what I mean.  Hold it up to a window on a bright day and look at the way light reflects off both surfaces.  There is a marked difference, and I think the hand-planed surface is more appealing.

However, using a hand plane forces you to understand wood grain.  Ignore that characteristic at your own peril when you approach the workpiece with a plane.   Plane in the wrong direction and you risk tearing out chunks of wood, adding untold hours to your project as you wonder how to repair the damage.  If you’re a hand tool user, wood grain plays a role in a lot of the decisions you make.  When you’re gluing up a panel for a table top, for example, you want the grain in each part of the top running the same way, or you must change the direction in which you plane.  And if you bookmatch a panel, you have introduced a grain reversal.  Nothing you can do about it, so think it through carefully.

In any event, a well-tuned hand plane with a sharp iron will make short work of marks left behind by saws, jointers and thickness planers.  They are most certainly worth the time and effort needed to learn to use them well.  As your skills and fussiness increase, you will find that scrapers can remove the little marks left by hand planes and yield a beautiful, smooth surface.

Sanding

Sanding will get rid of the machine marks, although it will be slower, noisier and much dustier.   There are some woods that are really difficult to plane; any species with interlocked grain falls in this group.  So plan extra time, make sure you wear hearing and eye protection and carefully plan a way to keep all that dust out of your lungs.  And while you’re at it, plan some extra time to clean up the dust from your shop before you start finishing, so the little dust nibs don’t fall out of the air onto your nicely sanded and now-wet-with-finish tabletop.

If I am forced to do a lot of sanding, I allow extra time in the schedule to account for dust.  Initially I try to minimize as much dust as I can by using vacuum attachments for power sanders, and by constantly vacuuming the surface as I finish hand-sanding.  Typically I will sand one day, allow another day for dust to settle out of the air, and vacuum my finishing area on the third day.  Finishing begins the day after.

As a rule of thumb, P220 is as far up the grit progression as you need to go on the bare wood.  As long as you have done a good job and were careful not to skip grits (remember that sandpapers are a system, and they are designed to work sequentially) going beyond P220 is a waste of time.  I strongly suggest that the final sanding step be done by hand rather than machine.  Sand with the grain, and sand carefully. Your objective is to ensure you haven’t left behind any of those little “pig-tails” that are the telltale of a random-orbit sander.

A Final Inspection

Before you put away the sander, the scraper or the hand planes, wipe down your project with denatured alcohol or naphtha.  Use the brief time before the solvent evaporates to carefully examine the surface for imperfections.  I like to use a bright light to help with this inspection, either a double halogen work light on a stand, or the sun through a window.  The light should come from in front of you, bounce off the work and then reflect into your eyes at a very shallow angle.  This is your last chance to catch a bit of tear-out, some glue that you missed, or any other blemish that will be magnified by finishing and top-coating.

Remember Those Cut-Offs?

If you saved cut-offs from the project, treat them the same way you are treating actual project components.  If you are sanding, sand the cut-offs with the same grits in the same progression.  If you are hand-planing, or scraping, do the same to your remnants.  This step is important, so don’t skip it.  While you’re at it, start making notes about what you are doing, and write them on the cutoff – on the side opposite the one you’re planing, scraping or sanding.  You will add to these notes later, so leave room to document additional steps.

In the next post we’ll talk about the assembly process and the final preparations for applying a finish.

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II

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Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon. He is a frequent woodworking instructor and writer.

Categories: Woodworking | Tags: , , , , | Leave a comment

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